Longitudinal Serological Surveillance for COVID-19 Antibodies after Infection and Vaccination.

The impact of COVID-19 is still felt around the world, and more information is needed regarding infection risk, vaccination responses, and the timing of booster vaccinations. We aimed to evaluate the association of vaccination with closely followed, longitudinal antibody titers and COVID-19 infection events. We conducted a natural history study in a convenience cohort in an ambulatory research unit. We measured anti-nucleocapsid and anti-spike antibody levels every 3 months for 1 year and captured weekly reports of medically confirmed COVID-19 infections. We analyzed the association of antibody titers with infection events as well as the association of the decision to receive vaccination with social, medical, and behavioral characteristics. 629 subjects were followed for 1 year, and 82.8% of them were vaccinated. 90 cases of medically confirmed COVID-19 infection were reported. Notable findings from our study include: an association of vaccination choice with social distancing, a qualitatively different anti-spike response in participants receiving the Ad26.COV2.S vaccine compared to those receiving mRNA vaccines, a muted anti-nucleocapsid response in breakthrough infections compared to unvaccinated infections, and the identification of a low antibody titer threshold associated with the risk of breakthrough infections. We conclude that, in a real-life setting, vaccination and social distancing behavior are positively correlated. The observed effect of vaccination in preventing COVID-19 may include both vaccine-mediated protection and the associated more cautious behavior exhibited by vaccinated individuals. In addition, we identified an antibody threshold associated with breakthrough infections in mRNA vaccinees, and this threshold may be used in medical decision-making regarding the timing of booster vaccinations. Therefore, our data may aid in the refinement of vaccination strategies during the COVID-19 pandemic. IMPORTANCE The COVID-19 pandemic continues to impact societies and health care systems worldwide and is continuously evolving. Immunity via vaccination or prior infection is the first and most important line of defense against COVID-19. We still do not have complete information on how vaccination-induced or infection-induced antibody titers change with time or on how this information can be used to guide decisions regarding booster vaccination. In a longitudinal observational study of a cohort of 629 subjects, 82% of breakthrough infections in vaccinees occurred when their anti-spike antibody titers were below 3,000 AU/mL. Our findings suggest that there may be an antibody threshold associated with breakthrough infections and that this threshold could possibly be used to aid decision-making regarding booster vaccinations. In addition, the use of anti-nucleocapsid antibody tiers may significantly underestimate the prevalence of breakthrough infections in vaccinated individuals.

The Launch of A Girl's First Period Study: Demystifying Reproductive Hormone Profiles in Adolescent Girls.

Limited data exist on the reproductive hormone dynamics that govern the transition from menarche to the establishment of the mature ovulatory cycles of a fertile young woman. It is also unclear how environmental and lifestyle factors could modulate this transition in contemporary girls. Here, we introduce A Girl's First Period Study, an ambitious longitudinal study aimed at charting the early post-menarchal course of a cohort of healthy girls in the Triangle region of North Carolina.

Development of a Machine Learning Model for the Estimation of Hip and Lumbar Angles in Ballet Dancers.

OBJECTIVE: Accurate field-based assessment of dance kinematics is important to understand the etiology, and thus prevention and management, of hip and back pain. The study objective was to develop a machine learning model to estimate thigh elevation and lumbar sagittal plane angles during ballet leg lifting tasks, using wearable sensor data. METHODS: Female dancers (n=30) performed ballet-specific leg lifting tasks to the front, side, and behind the body. Dancers wore six wearable sensors (100 Hz). Data were simultaneously collected using an 18-camera motion analysis system (250 Hz). Due to synchronization and hardware malfunction issues, only 23 dancers had usable data. Using leave-one-out cross-validation, machine learning models were compared with the optic motion capture system using root mean square error (RMSE) in degrees and correlation coefficients (r) over the complete movement profile of each leg lift and mean absolute error (MAE) and Bland Altman plots for peak angle accuracy. RESULTS: The average RMSE for model estimation was 6.8° for thigh elevation angle and 5.6° for lumbar spine sagittal plane angle, with respective MAE of 6.3°and 5.7°. There was a strong correlation between the machine learning model and optic motion capture for peak angle values (thigh r=0.86, lumbar r=0.96). CONCLUSION: The models developed demonstrated an acceptable degree of accuracy for the estimation of thigh elevation angle and lumbar spine sagittal plane angle during dance-specific leg lifting tasks. This provides potential for a near-real-time, field-based measurement system.

Dancers' Joint Strategies for Achieving Turnout in Low and High Friction Conditions.

BACKGROUND: Dancing with legs externally rotated (turnout) is a fundamental element of ballet technique. A reliance on floor friction to achieve turnout may contribute toward the high injury rate in dancers. Joint strategies used by dancers in high and low friction turnout conditions are not well understood. OBJECTIVES: To quantify the lower limb and lumbar spine joint strategies used by female pre-professional dancers to achieve turnout in low-friction (rotation discs) and high-friction (functional and forced) conditions. METHODS: Twenty-three pre-professional female dancers participated in the study. A 12-camera motion analysis system collected hip and knee external rotation (ER), ankle abduction, and lumbar extension angles in three turnout conditions and passive hip ER range of motion angles. Repeated measures ANOVA analysed the differences between joint angles, maximum turnout angle (foot relative to pelvis), and available hip ER. RESULTS: Dancers demonstrated lower knee ER (18.5±4.8°) and ankle abduction (6.0±7.7°) angles during low-friction turnout compared to higher friction conditions (p<0.05). Dancers utilised between 70-83% of available hip ER within all conditions. Low-friction turnout demonstrated greater hip ER contribution within maximum turnout (43%) compared to higher friction conditions. Dancers demonstrated greater lumbar extension angles in low-friction turnout compared to higher friction conditions (p<0.05). CONCLUSIONS: Further hip ER strength training is required to promote greater hip ER range within the position. Rotation discs may be a valuable training tool as dancers demonstrated greater hip ER utilisation with less knee ER and ankle abduction; however, this position did promote undesirable lumbar extension.

Mulligan Knee Taping Using Both Elastic and Rigid Tape Reduces Pain and Alters Lower Limb Biomechanics in Female Patients With Patellofemoral Pain.

BACKGROUND: Evidence supports the use of Mulligan knee taping in managing patellofemoral pain (PFP). However, no studies have compared the efficacy of rigid and elastic tape using this technique. HYPOTHESIS: Mulligan knee taping applied with both rigid and elastic tape will produce similar reductions in knee pain, hip internal rotation, and knee flexion moments compared with no tape. Elastic tape will also be more comfortable than rigid tape. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 19 female patients (mean age, 26.5 ± 4.5 years) with PFP performed a self-selected pain provocative task, single-leg squat (SLSq) task, and running task while wearing Mulligan knee taping applied with rigid tape, elastic tape at 100% tension, and no tape. Pain and taping comfort were recorded using 11-point numeric rating scales. An 18-camera motion capture system and in-ground force plates recorded 3-dimensional lower limb kinematics and kinetics for the SLSq and running tasks. Statistical analysis involved a series of repeated-measures analyses of variance. The Wilcoxon signed rank test was used for analyzing taping comfort. RESULTS: Compared with no tape, both rigid and elastic tape significantly reduced pain during the pain provocative task (mean difference [MD], -0.97 [95% CI, -1.57 to -0.38] and -1.42 [95% CI, -2.20 to -0.64], respectively), SLSq (MD, -1.26 [95% CI, -2.23 to -0.30] and -1.13 [95% CI, -2.09 to -0.17], respectively), and running tasks (MD, -1.24 [95% CI, -2.11 to -0.37] and -1.16 [95% CI, -1.86 to -0.46], respectively). Elastic tape was significantly more comfortable than rigid tape generally (P = .005) and during activity (P = .022). Compared with no tape, both rigid and elastic tape produced increased knee internal rotation at initial contact during the running task (MD, 5.5° [95% CI, 3.6° to 7.4°] and 5.9° [95% CI, 3.9° to 7.9°], respectively) and at the commencement of knee flexion during the SLSq task (MD, 5.8° [95% CI, 4.5° to 7.0°] and 5.8° [95% CI, 4.1° to 7.4°], respectively), greater peak knee internal rotation during the running (MD, 1.8° [95% CI, 0.4° to 3.3°] and 2.2° [95% CI, 0.9° to 3.6°], respectively) and SLSq tasks (MD, 3.2° [95% CI, 2.1° to 4.3°] and 3.8° [95% CI, 2.3° to 5.2°], respectively), and decreased knee internal rotation range of motion during the running (MD, -3.6° [95% CI, -6.1° to -1.1°] and -3.7° [95% CI, -6.2° to -1.2°], respectively) and SLSq tasks (MD, -2.5° [95% CI, -3.9° to -1.2°] and -2.0° [95% CI, -3.2° to -0.9°], respectively). CONCLUSION: Mulligan knee taping with both rigid and elastic tape reduced pain across all 3 tasks and altered tibiofemoral rotation during the SLSq and running tasks. CLINICAL RELEVANCE: Both taping methods reduced pain and altered lower limb biomechanics. Elastic tape may be chosen clinically for comfort reasons.

An Exploration of Machine-Learning Estimation of Ground Reaction Force from Wearable Sensor Data.

This study aimed to develop a wearable sensor system, using machine-learning models, capable of accurately estimating peak ground reaction force (GRF) during ballet jumps in the field. Female dancers (n = 30) performed a series of bilateral and unilateral ballet jumps. Dancers wore six ActiGraph Link wearable sensors (100 Hz). Data were collected simultaneously from two AMTI force platforms and synchronised with the ActiGraph data. Due to sensor hardware malfunctions and synchronisation issues, a multistage approach to model development, using a reduced data set, was taken. Using data from the 14 dancers with complete multi-sensor synchronised data, the best single sensor was determined. Subsequently, the best single sensor model was refined and validated using all available data for that sensor (23 dancers). Root mean square error (RMSE) in body weight (BW) and correlation coefficients (r) were used to assess the GRF profile, and Bland-Altman plots were used to assess model peak GRF accuracy. The model based on sacrum data was the most accurate single sensor model (unilateral landings: RMSE = 0.24 BW, r = 0.95; bilateral landings: RMSE = 0.21 BW, r = 0.98) with the refined model still showing good accuracy (unilateral: RMSE = 0.42 BW, r = 0.80; bilateral: RMSE = 0.39 BW, r = 0.92). Machine-learning models applied to wearable sensor data can provide a field-based system for GRF estimation during ballet jumps.

The Difference in Lower Limb Landing Kinematics Between Adolescent Dancers and Non-Dancers.

The high prevalence of lower limb overuse injuries among adolescent ballet dancers may be due in part to repetitive land- ings. This cross-sectional study compared how adolescent ballet dancers perform a drop-landing task in comparison to non-dancers in order to help understand injury mechanics. Fifteen adolescent female ballet dancers aged 11.9 ± 1.1 years and 17 non-dancers aged 10.9 ± 0.9 years each performed three single limb drop-landings from a 30 cm box. An 18-camera motion capture system (Vicon MX; Oxford Metrics, Oxford, UK; 250 Hz) and a force platform (Advanced Mechanical Technology Inc., Watertown, Massachusetts, USA; 2,000 Hz) were used to collect lower limb joint angles in all three planes of motion and peak vertical ground reaction forces during the landing phase. These variables were compared for the two sets of participants using independent samples t-tests (p < 0.01). While the dancers landed with greater sagittal plane range of motion, this appeared to provide no mechanical advantage with no reduction in ground reaction force. Rather, the increased sagittal range of motion was coupled with increased coronal and frontal plane motion. This may place dancers at increased risk of injury.

Deceleration characteristics of elite Australian male field hockey players during an Olympic tournament.

OBJECTIVES: This study described the deceleration efforts of the Australian men's field hockey team during the 2016 Olympics by categorising efforts into 'bands' of intensity; and comparing the deceleration intensity and frequency by player position, game period and opponent. DESIGN: Descriptive retrospective analysis. METHODS: Global positioning system sensors (MinimaxX S4, Catapult Sports Pty. Ltd., Melbourne, Australia; 10Hz) were worn by 15 male field hockey players during six games of the 2016 Olympic tournament. RESULTS: There were 8998 individual deceleration efforts (≤-3ms-2) performed over the tournament with the most intense effort measured at -13.6ms-2. Deceleration intensity 'bands' were calculated using Receiver Operator Characteristic (ROC) curves as low intensity=-3 to -5.99ms-2; medium intensity=-6 to -8.99ms-2; high intensity=-9 to -11.99ms-2; and, very high intensity=<-12ms-2. There were no significantly different decelerations between field positions but decelerations performed within game period one were more intense than game period two (-0.11±0.01ms-2, p<0.001). Deceleration efforts were more frequent in game period one than two [X2(3, N=8997)=12.00, p=0.007]. CONCLUSIONS: Decelerations are common in elite field hockey and very high intensities are present. These findings, in conjunction with other metrics can be used as a tool to monitor the load associated with training and match play in field hockey.

Differences in lower limb biomechanics between ballet dancers and non-dancers during functional landing tasks.

OBJECTIVES: To determine the differences in the lower limb landing biomechanics of adolescent ballet dancers compared to non-dancers when performing a hop and a stop jump task. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Thirteen adolescent female ballet dancers (11.8 ±â€¯1.1 years) and 17 non-dancers (10.9 ±â€¯0.8 years) performed hop and stop jump tasks. MAIN OUTCOME MEASURES: Vertical ground reaction force, and three-dimensional ankle, knee and hip joint angles and moments during the landing phase. RESULTS: Dancers displayed greater sagittal plane joint excursions during the hop and stop jump at the ankle (mean difference = 22.0°, P < 0.001, 14.8°, P < 0.001 respectively), knee (mean difference = 18.1°, P = 0.001, 9.8°, P = 0.002 respectively) and hip (stop jump task; mean difference = 8.3°, P = 0.008). Dancers displayed a larger hip extensor moment compared to non-dancers (P < 0.001) during the stop jump task only. Dancers also took longer to reach peak vGRF and jumped three times higher than non-dancers (P < 0.001) during the stop jump task. No difference in peak vGRF between groups was displayed for either task. CONCLUSIONS: Adolescent dancers demonstrate a transfer of landing technique to non-ballet specific tasks, reflective of the greater jump height and sagittal plane joint excursions. This landing strategy may be associated with the low rate of non-contact ACL injuries in female dancers.

Effect of prophylactic ankle taping on ankle and knee biomechanics during basketball-specific tasks in females.

OBJECTIVE: The aim of this study was to investigate the effects of ankle taping on ankle and knee joint biomechanics during cutting and rebound activities in females. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Twenty semi-professional female basketball players performed a cut and rebound task under two conditions (taped and no-tape). MAIN OUTCOME MEASURES: Kinematic and ground reaction force data were collected during the deceleration phase of each movement task. RESULTS: Taping resulted in a significant reduction in peak ankle dorsiflexion, inversion and internal rotation angles and range of motion (ROM) at the ankle joint; and reduced knee ROM in the sagittal plane during the rebound task only. Taping significantly reduced peak knee flexion moment (0.29 Nm/kg, P = 0.013) and increased knee internal rotation moment (0.63 Nm/kg, P = 0.026) during the cutting task compared to control. Taping also significantly reduced the internal rotation moment (0.07 Nm/kg, P = 0.025), and medial shear forces (0.14 N/kg, P = 0.012) in the rebound task. CONCLUSION: Results of the study suggest that ankle taping restrict ankle range of movement in the rebound task only and ankle taping appears to have upstream effects on the knee, which may have injury implications.

On using wearable tri-axial accelerometers to examine the striking phase kinematics of expert specialist drag flickers on-field.

Analysing player kinematics during a match using "gold-standard" 3D video-based motion analysis techniques is a difficult prospect indeed. The development of small, wireless, wearable sensors offers the potential to reduce the challenges of measuring kinematics during match-play without hindering performance. The present study examined the viability of using wireless tri-axial accelerometers to examine whether key performance measures of drag flicks executed by expert specialist drag-flickers are predicted by the kinematics of the striking phase. Linear mixed models were used to examine whether the speed and accuracy of players' drag flicks were predicted by the duration of stick-ball contact, and the kinematics of the lead lower limb at stick-ball contact and ball release. Results revealed that stick and lead lower limb kinematics significantly predicted shot accuracy but not shot speed. Shorter drag-time predicted more accurate flicks (p = 0.03) as did a more vertical leg at stick-ball contact (p = 0.016) and a more horizontal thigh at ball release (p = 0.001). This may indicate that there are more ways to produce fast drag flicks than accurate ones. This study illustrates that wireless tri-axial accelerometers can be used on-field to measure the effects of kinematics on key performance measures.

A biomechanical comparison in the lower limb and lumbar spine between a hit and drag flick in field hockey.

Research has revealed that field hockey drag flickers have greater odds of hip and lumbar injuries compared to non-drag flickers (DF). This study aimed to compare the biomechanics of a field hockey hit and a specialised field hockey drag flick. Eighteen male and seven female specialised hockey DF performed a hit and a drag flick in a motion analysis laboratory with an 18-camera three-dimensional motion analysis system and a calibrated multichannel force platform to examine differences in lower limb and lumbar kinematics and kinetics. Results revealed that drag flicks were performed with more of a forward lunge on the left lower limb resulting in significantly greater left ankle dorsiflexion, knee, hip and lumbar flexion (Ps<0.001) compared to a hit. Drag flicks were also performed with significantly greater lateral flexion (P < 0.002) and rotation of the lumbar spine (P < 0.006) compared to a hit. Differences in kinematics lead to greater shear, compression and tensile forces in multiple left lower limb and lumbar joints in the drag flick compared to the hit (P < 0.05). The biomechanical differences in drag flicks compared to a hit may have ramifications with respect to injury in field hockey drag flickers.

Lower Limb and Trunk Biomechanics After Fatigue in Competitive Female Irish Dancers.

CONTEXT: Because of the increasing popularity of participation in Irish dance, the incidence of lower limb injuries is high among this competitive population. OBJECTIVE: To investigate the effects of fatigue on the peak lower limb and trunk angles as well as the peak lower limb joint forces and moments of competitive female Irish dancers during the performance of a dance-specific single-limb landing. DESIGN: Cross-sectional study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Fourteen healthy, female, competitive Irish dancers (age = 19.4 ± 3.7 years, height = 165.3 ± 5.9 cm, mass = 57.9 ± 8.2 kg). INTERVENTION(S): Participants performed an Irish dance-specific leap before and after a dance-specific fatigue protocol. During each landing movement, 3-dimensional lower limb kinematics (250 Hz) and ground reaction forces (1000 Hz) were collected. Paired t tests were performed to determine the differences (P ≤ .05) in lower limb and trunk biomechanics prefatigue and postfatigue. MAIN OUTCOME MEASURE(S): Peak lower limb and trunk angles as well as peak lower limb joint reaction forces and external moments. RESULTS: Compared with the prefatigue trials, dancers landed with reduced ankle plantar flexion (P = .003) and hip external rotation (P = .007) and increased hip-adduction alignment (P = .034) postfatigue. Dancers displayed greater anterior shear (P = .003) and compressive (P = .024) forces at the ankle and greater external knee-flexion moments (P = .024) during the postfatigue compared with the prefatigue landing trials. CONCLUSIONS: When fatigued, dancers displayed a decline in landing performance in terms of aesthetics as well as increased ankle- and knee-joint loading, potentially exposing them to a greater risk of injuries.

Higher anterior knee laxity influences the landing biomechanics displayed by pubescent girls.

Despite an increase in anterior knee laxity (AKL) during the adolescent growth spurt in girls, it is unknown whether landing biomechanics are affected by this change. This study investigated whether pubescent girls with higher AKL displayed differences in their lower limb strength or landing biomechanics when performing a horizontal leap movement compared to girls with lower AKL. Forty-six pubescent girls (10-13 years) were tested at the time of their peak height velocity (PHV). Passive AKL was quantified and used to classify participants into higher (HAKL; peak displacement > 4 mm) and lower (LAKL; peak displacement < 3 mm) AKL groups (n = 15/group). Three-dimensional kinematics, ground reaction forces (GRF) and muscle activation patterns were assessed during a horizontal leap landing. HAKL participants displayed significantly (P < 0.05) reduced hip abduction, increased hip abduction moments, as well as earlier hamstring muscle and later tibialis anterior activation compared to LAKL participants. Girls with HAKL displayed compensatory landing biomechanics, which are suggested to assist the functional stability of their knees during this dynamic task. Further research is warranted, however, to confirm or refute this notion.

Does skill specialisation influence individual differences in drag flicking speed and accuracy?

Research has revealed that individual soccer goalkeepers respond differently to penalty shots, depending on their specific perceptual and motor capabilities. However, it remains unclear whether analogous differences exist between individual penalty takers, and if specialising in penalty taking affects the occurrence of differences between individuals. The present study examined individual differences in penalty shot speed and accuracy for specialists in penalty taking versus non-specialists. Expert specialist field hockey drag flickers and equivalently skilled non-specialists performed drag flicks towards predetermined targets placed in the face of a standard field hockey goal. Comparisons in shot speed and accuracy were made at a group level (specialists vs. non-specialists) as well as between individuals. Results revealed differences in both speed and accuracy between specialists, but only differences in speed between non-specialists. Specialists generated significantly greater shot speed than non-specialists (P < .001) and were more accurate to some, but not all, targets (top left, P < .006, bottom left P < .001). In addition, it was found that in specialists increasing practice correlated with decreasing accuracy. This may indicate that excessive practice could potentially reduce a specialist's accuracy in shooting towards specific targets.

Effect of External Ankle Support on Ankle and Knee Biomechanics During the Cutting Maneuver in Basketball Players.

BACKGROUND: Despite the high prevalence of lower extremity injuries in female basketball players as well as a high proportion of athletes who wear ankle braces, there is a paucity of research pertaining to the effects of ankle bracing on ankle and knee biomechanics during basketball-specific tasks. PURPOSE: To compare the effects of a lace-up brace (ASO), a hinged brace (Active T2), and no ankle bracing (control) on ankle and knee joint kinematics and joint reaction forces in female basketball athletes during a cutting maneuver. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty healthy, semi-elite female basketball players performed a cutting task under both ankle brace conditions (lace-up ankle brace and hinged ankle brace) and a no-brace condition. The 3-dimensional kinematics of the ankle and knee during the cutting maneuver were measured with an 18-camera motion analysis system (250 Hz), and ground-reaction force data were collected by use of a multichannel force plate (2000 Hz) to quantify ankle and knee joint reaction forces. Conditions were randomized using a block randomization method. RESULTS: Compared with the control condition, the hinged ankle brace significantly restricted peak ankle inversion (mean difference, 1.7°; P = .023). No significant difference was found between the lace-up brace and the control condition ( P = .865). Compared with the lace-up brace, the hinged brace significantly reduced ankle and knee joint compressive forces at the time of peak ankle dorsiflexion (mean difference, 1.5 N/kg [ P = .018] and 1.4 N/kg [ P = .013], respectively). Additionally, the hinged ankle brace significantly reduced knee anterior shear forces compared with the lace-up brace both during the deceleration phase and at peak ankle dorsiflexion (mean difference, 0.8 N/kg [ P = .018] and 0.9 N/kg [ P = .011], respectively). CONCLUSION: The hinged ankle brace significantly reduced ankle inversion compared with the no-brace condition and reduced ankle and knee joint forces compared with the lace-up brace in a female basketball population during a cutting task. Compared with the lace-up brace, the hinged brace may be a better choice of prophylactic ankle support for female basketball players from a biomechanical perspective. However, both braces increased knee internal rotation and knee abduction angles, which may be problematic for a population that already has a high prevalence of knee injuries.

The Effect of the Mulligan Knee Taping Technique on Patellofemoral Pain and Lower Limb Biomechanics.

BACKGROUND: Patellofemoral pain (PFP) affects 25% of the general population, occurring 2 times more often in females compared with males. Taping is a valuable component of the management plan for altering lower limb biomechanics and providing pain relief; however, the effects of alternative taping techniques, such as Mulligan knee taping, appear yet to be researched. PURPOSE: To determine whether the Mulligan knee taping technique altered levels of perceived knee pain and lower limb biomechanics during a single-legged squat (SLSq) in adult females with PFP. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 20 female patients with PFP, aged 18 to 35 years, participated in this study. Participants performed 3 to 5 SLSq on their most symptomatic limb during a taped (Mulligan knee taping technique) and nontaped (control) condition. During the eccentric phase of the SLSq, the 3-dimensional kinematics (250 Hz) of the knee and hip and the ground-reaction forces (1000 Hz) and muscle activation patterns (1000 Hz) of the gluteus medius, vastus lateralis, and vastus medialis oblique were measured. Participants' perceived maximum knee pain was also recorded after the completion of each squat. RESULTS: Between-condition differences were found for hip kinematics and gluteus medius activation but not for kinetics or vastus medialis oblique and vastus lateralis muscle activity (timing and activation). Compared with the nontaped condition, the Mulligan knee taping technique significantly (P = .001) reduced perceived pain during the SLSq (mean ± SD: 2.29 ± 1.79 and 1.29 ± 1.28, respectively). In the taped condition compared with the control, the onset timing of the gluteus medius occurred significantly earlier (120.6 ± 113.0 and 156.6 ± 91.6 ms, respectively; P = .023) and peak hip internal rotation was significantly reduced (6.38° ± 7.31° and 8.34° ± 7.92°, respectively; P = .002). CONCLUSION: The Mulligan knee taping technique successfully reduced knee pain in participants with PFP. This is the first study to establish a link between Mulligan knee taping and the reduction of PFP in conjunction with decreased hip internal rotation and earlier activation of gluteus medius. CLINICAL RELEVANCE: The Mulligan knee taping technique may benefit the clinical environment by providing an alternative evidence-based treatment plan for PFP.

How Young Girls Change Their Landing Technique Throughout the Adolescent Growth Spurt.

BACKGROUND: Despite the rapid musculoskeletal changes experienced by girls throughout the adolescent growth spurt, little is known about how their lower limb landing technique changes during this time. PURPOSE: To investigate the longitudinal changes in the 3-dimensional lower limb kinematics, joint moments, and muscle activation patterns displayed by girls when performing a horizontal landing task throughout their adolescent growth spurt. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 33 healthy 10- to 13-year-old girls, in Tanner stage II, with a maturity offset of -6 to -4 months (time from peak height velocity) were recruited. According to her maturity offset, each participant was tested up to 4 times during the 12 months of her growth spurt (maturity offset: test 1 = -6 to -4 months; test 2 = 0 months; test 3 = 4 months; test 4 = 8 months). During each test session, participants performed a horizontal leap movement, during which ground-reaction forces (1000 Hz), lower limb muscle activity (1000 Hz), and kinematic data (100 Hz) were collected. RESULTS: Throughout the growth spurt, girls displayed a decrease in knee flexion (P = .028), increase in hip flexion (P = .047), increase in external knee abduction moments (P = .008), and decrease in external hip adduction moments (P = .003) during the landing movement. CONCLUSION: During their adolescent growth spurt, pubescent girls displayed a change in the strategy with which they controlled their lower limb to land after performing a horizontal leap movement. This change in the landing strategy has the potential to increase the risk of anterior cruciate ligament injuries toward the latter stages of the adolescent growth spurt. CLINICAL RELEVANCE: The outcomes of this research provide a greater understanding of the changes in the landing strategy used by pubescent girls throughout the adolescent growth spurt. This can assist in the development of screening tools designed to determine "at-risk" landing biomechanics during puberty.

The prevalence and severity of injuries in field hockey drag flickers: a retrospective cross-sectional study.

The drag flick is the preferred method of scoring during a penalty corner in field hockey. Performing the drag flick requires a combination of strength, coordination and timing, which may increase susceptibility to injuries. However, injury prevalence in drag flickers has not previously been investigated. Therefore, this study compared the injury prevalence and severity of lower limb and lower back injuries between drag flickers and non-drag flickers in field hockey. A total of 432 local, national and international adult field hockey players (242 males, 188 females) completed an online questionnaire to retrospectively determine the 3-month prevalence and severity of ankle, knee, hip and lower back injuries. Of this group, 140 self-identified as drag flickers and 292 as non-drag flickers. The results showed that drag flickers had significantly higher prevalence of hip (OR: 1.541; 95% CI: 1.014, 2.343) and lower back injury (OR: 1.564; 95% CI: 1.034, 2.365) compared to non-drag flickers. No significant differences were observed between drag flickers and non-drag flickers in injury prevalence at the ankle and knee. There were no significant between-group differences in injury severity scores. Overall, the prevalence of hip and lower back injuries was significantly higher in drag flickers compared to non-drag flickers.